<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			#box{height: 100px;width: 100px;}
		</style>
	</head>
	<body>
		<div id="box"></div>
	</body>
	<script type="text/javascript">
		var oId = document.getElementById('box')
		alert(oId.offsetHeight)
	</script>
</html>
